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The Role of Sleep in Product Choice

AMHERST, Mass. – Conventional wisdom, not to mention Mom, says that when one needs to make a sound decision, it’s a good idea to sleep on it. But while sleep has been shown to benefit some cognitive tasks such as problem-solving, its impact on everyday choices is less clear, say neuroscientists Rebecca Spencer at the University of Massachusetts Amherst and Uma Karmarkar of the Harvard Business School.

Now they offer experimental results suggesting that normal nighttime sleep gave shoppers more positive feelings about their purchasing choices, but sleep failed to help them feel more confident about their decision. Further, sleep seemed to make participants reluctant to commit to spending money on an item they had considered buying the day before. Results appear in the Journal of Behavioral Decision Making.

Spencer says, “When we think of the phrase ‘sleep on it,’ we think that sleep will point us to an answer. So our assumption was that participants would be more confident in their decisions after sleep, but this wasn’t the case.”

In the first of two experiments, Karmarkar and Spencer simulated an online shopping experience by presenting 62 research subjects ages 18 to 36 with products and their attributes. Subjects could choose between four laptop satchels 12 hours later, at the end of session 2, and some of them would win the satchel of their choice by random drawing. Half the participants viewed the bags at the start of their day (Wake group) while the other half looked at the bags between 8 and 10 p.m. before sleeping (Sleep group). They were also shown satchel brand names paired with some positive (spacious, trendy) and less positive attributes (not waterproof) of each.

The authors report that “when participants browsed the bags in the evening, they remembered more positive attributes the following morning, after 12 hours with sleep, than when they browsed in the morning and recall was tested following 12 hours of wakefulness.”

In the second experiment, the researchers considered whether sleep’s ability to consolidate and amplify subjects’ memory for positive product attributes influenced their purchase decisions. Spencer and Karmarkar therefore used a similar experimental setup as before, but included four more clearly negative product descriptors along with the four positive words in the attributes.

They found that “despite the sleep period leading to an overall bias toward positive thoughts about the choice set, participants in the Sleep group showed significantly less increase in desire to purchase their preferred satchel across sessions compared to those in the Wake group.”

They add, “While more positive information might seem to favor making a decision and decision confidence, subjects were more reluctant to make a decision following sleep.” Participants in both experiments expressed less interest in buying their preferred item when they had slept during the time between learning about options and making the choice.

This investigation suggests sleep may have a tempering effect on impulse buying. “Sleep makes us more rational about the decision,” Spencer notes. “Rather than asking ourselves whether we should buy camera A or camera B, after sleeping on it, we might ask whether I really need a new camera after all.”

Spencer, a sleep expert, and Karmarkar, who has studied the neural and behavioral impact of various product factors on decision-making, conclude that, “being more knowledgeable about the products led to greater internal conflict regarding the choices.” They add that while earlier studies considered whether time away from the task, that is, taking a break from shopping, could aid decisions, theirs is the first to consider the role of “sleep in the offline interval” on product choice.